cli: add `--timeout` persistent flag for parity with CQ_TIMEOUT

[peteski22]

Summary

The CLI operation timeout is configurable only via the CQ_TIMEOUT environment variable — there is no --timeout persistent flag. This is inconsistent with the other core connection settings (--addr, --api-key, --db-path), each of which is exposed as both a persistent flag and an environment variable.

Current behavior

• cliTimeout() (cli/cmd/cli.go) reads CQ_TIMEOUT (integer seconds), falling back to defaultCLITimeout (30s).
• InitFlags() registers --addr, --api-key, --db-path, but no timeout flag.

Proposed

• Register a --timeout persistent flag in InitFlags(), resolving with the usual precedence: flag > env (CQ_TIMEOUT) > default.
• Have cliTimeout() consider the flag value.
• Document it in the flag help text (env: CQ_TIMEOUT), matching the existing flags.

Open question

• Flag type: time.Duration (e.g. --timeout 30s) reads naturally and is Go-idiomatic, but CQ_TIMEOUT is currently integer seconds. Decide whether to keep both as seconds for consistency, or accept a duration on the flag while the env var stays seconds.

Context

Surfaced during review of #516, which fixed the remote HTTP client ignoring CQ_TIMEOUT. The flag gap is orthogonal to that fix and better handled on its own.